The present technology relates generally to engines and, in particular, to methods and systems for an engine having differential fueling between donor and non-cylinders operating with exhaust gas recirculation (EGR).
A dual-fuel engine is an alternative internal combustion engine designed to run on more than one fuel each stored in separate vessels. Dual fuel engines are known for various applications, such as generator sets, engine-driven compressors, engine driven pumps, machine, off-highway trucks, locomotives, and others. Such engines are capable of burning varying proportions of the resulting blend of fuels in the combustion chamber and the fuel injection or spark timing may be adjusted according to the blend of fuels in the combustion chamber. The operation of such engines by substitution of a certain amount of heavy fuel, such as diesel, with a lighter fuel, such as natural gas, biogas, liquid petroleum gas (LPG) or other types of fuel that may be more readily available and cost effective, makes them more effective to operate.
However, those engines having donor cylinders operate at higher exhaust pressure for the donor cylinders, resulting in increased exhaust gas residuals, potentially causing knock in the donor cylinders. Also, the increased exhaust gas residuals limit the attainable substitution rate in the dual fuel engines since lighter fuels such as natural gas are more susceptible to knock. Further, the exhaust emissions generally include pollutants such as carbon oxides (e.g., carbon monoxide), nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM). The amount and relative proportion of these pollutants varies according to the fuel-air mixture, compression ratio, injection timing, environmental conditions (e.g., atmospheric pressure, temperature, etc.), and the like.
There is therefore a desire for an improved system and method for operating engines.